Initiating preparations for engine autostop prior to vehicle stop

ABSTRACT

A stop/start vehicle includes at least one controller that, in response to predicting a vehicle stop, initiates an engine pre-shutdown protocol such that vehicle subsystems begin to prepare for engine shutdown prior to a speed of the vehicle reaching approximately zero to reduce time between the speed of the vehicle reaching approximately zero and engine shutdown.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional of U.S. application Ser. No.13/568,187, filed Aug. 7, 2012, the disclosure of which is herebyincorporated in its entirety by reference herein.

TECHNICAL FIELD

This disclosure relates to micro-hybrid or stop/start vehicles andinitiating activities associated with engine shutdown prior to vehiclestop.

BACKGROUND

A micro-hybrid or stop/start vehicle can selectively turn its engine offduring portions of a drive cycle to conserve fuel. As an example, astop/start vehicle can turn its engine off while the vehicle is stoppedrather than allow the engine to idle. The engine can then be restarted,for example, when a driver releases the brake pedal or steps on theaccelerator pedal.

SUMMARY

A vehicle includes an engine, a vehicle component, and at least onecontroller. The at least one controller issues auto stop commands andauto start commands. The engine is shutdown in response to the auto stopcommands and started in response to the auto start commands. The atleast one controller, in response to predicting a vehicle stop, furtherinitiates an engine pre-shutdown protocol such that the vehiclecomponent begins to prepare for engine shutdown prior to a speed of thevehicle reaching approximately zero to reduce time between the speed ofthe vehicle reaching approximately zero and engine shutdown. The vehiclecomponent may be an intake manifold in fluid communication with theengine and beginning to prepare for engine shutdown may includebeginning a purge of the intake manifold. The vehicle component may bean electrical bus and beginning to prepare for engine shutdown mayinclude beginning to reduce a voltage on the electrical bus to apredetermined value. The vehicle component may be an automatictransmission mechanically coupled with the engine and beginning toprepare for engine shutdown may include beginning to shift gears of theautomatic transmission. The vehicle component may be an electric pumpand beginning to prepare for engine shutdown may include beginning toactivate the electric pump.

A stop/start vehicle includes an engine, an electrical bus, and at leastone controller. The at least one controller initiates a reduction involtage on the electrical bus to a predetermined value when a speed ofthe vehicle is greater than approximately zero and less than apredetermined speed. The at least one controller also initiates a stopof the engine after the speed of the vehicle is approximately zero andthe voltage is approximately equal to the predetermined value. Thestop/start vehicle may further include an intake manifold in fluidcommunication with the engine and the at least one controller mayfurther initiate a purge of the intake manifold when the speed of thevehicle is greater than approximately zero and less than thepredetermined speed. The stop/start vehicle may further include anautomatic transmission mechanically coupled with the engine and the atleast one controller may further initiate a shifting of gears of theautomatic transmission when the speed of the vehicle is greater thanapproximately zero and less than the predetermined speed. The stop/startvehicle may further include an electric pump and the at least onecontroller may further initiate activation of the electric pump when thespeed of the vehicle is greater than approximately zero and less thanthe predetermined speed.

A method for operating a stop/start vehicle includes in response topredicting a vehicle stop, initiating engine pre-shutdown preparationsfor at least one vehicle component prior to vehicle speed reachingapproximately zero to reduce time between the vehicle speed reachingapproximately zero and shutting down the engine. The method furtherincludes in response to the vehicle speed reaching approximately zeroand completion of the engine pre-shutdown preparations, shutting downthe engine. The at least one vehicle component may be an intake manifoldin fluid communication with the engine and initiating enginepre-shutdown preparations may include initiating a purge of the intakemanifold. The at least one vehicle component may be an electrical busand initiating engine pre-shutdown preparations may include initiating areduction in voltage on the electrical bus to a predetermined value. Theat least one vehicle component may be an automatic transmissionmechanically coupled with the engine and initiating engine pre-shutdownpreparations may include initiating a shifting of gears of the automatictransmission. The at least one vehicle component may be an electric pumpand initiating engine pre-shutdown preparations may include initiatingactivation of the electric pump.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a stop/start vehicle.

FIGS. 2, 3 and 4 are flowcharts illustrating portions of algorithms forcontrolling a stop/start vehicle.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described herein. It is to beunderstood, however, that the disclosed embodiments are merely examplesand other embodiments can take various and alternative forms. Thefigures are not necessarily to scale; some features could be exaggeratedor minimized to show details of particular components. Therefore,specific structural and functional details disclosed herein are not tobe interpreted as limiting, but merely as a representative basis forteaching one skilled in the art to variously employ the presentinvention. As those of ordinary skill in the art will understand,various features illustrated and described with reference to any one ofthe figures can be combined with features illustrated in one or moreother figures to produce embodiments that are not explicitly illustratedor described. The combinations of features illustrated providerepresentative embodiments for typical applications. Variouscombinations and modifications of the features consistent with theteachings of this disclosure, however, could be desired for particularapplications or implementations.

Vehicle systems that are directly or indirectly influenced by operationof an engine are often prepared for an engine shutdown. That is, certainvehicle systems perform specified activities prior to engine shutdown.For example, an intake manifold may be purged to improve subsequentengine restart smoothness, a voltage on an electrical bus may be rampeddown to reduce power consumption by electrical loads during engine off,an automatic transmission may shift gears in anticipation of vehiclelaunch after engine restart, an electric pump may be activated tomaintain transmission line pressure during engine off, etc. Certain ofthese activities, such as purging the intake manifold, can be performedin fractions of a second while others, such as ramping down the voltageof the electrical bus, can take several seconds to complete. Hence, ifthese activities are initiated after vehicle speed has reached zero,valuable engine off time could be lost to pre-engine shut downprotocols. Put another way, increasing the duration of time during whichthe engine is stopped while vehicle speed zero can increase fuel savingsand emissions reductions.

Certain systems, methods, algorithms, etc. disclosed herein can predictvehicle stops during a drive cycle and initiate engine pre-shutdownprotocols prior to vehicle speed reaching zero so that the engine can beoff for longer periods of time while the vehicle speed is zero.

Referring to FIG. 1, an automotive vehicle 10 includes an engine 12, atransmission 14 and an alternator 16 each mechanically coupled with theengine 12 as indicated by heavy solid line. The vehicle 10 also includesan intake manifold 18 in fluid communication with the engine 12, anelectric pump 20 in fluid communication with the transmission 14, and afluid reservoir 22 in fluid communication with electric pump 20 asindicated by heavy dashed line. The vehicle 10 further includes abattery 24, an electrical bus 26, electrical loads 28 (e.g., a resistiveheating element, infotainment systems, etc.), an accelerator pedal 30, abrake pedal 32, vehicle speed sensors 34, and one or more controllers36. The alternator 16, electric pump 20, battery 24, and electricalloads 28 are electrically connected with the electrical bus 26 asindicated by thin dashed line. The engine 12, transmission 14, manifold18, battery 24, electrical bus 26, accelerator pedal 30, brake pedal 32,and speed sensors 34 are in communication with/under the control of thecontrollers 36 as indicated by thin solid line. Other vehiclearrangements, of course, are also possible.

The controllers (or stop/start system) 36 can issue auto stop commands(e.g., commands to stop the engine 12 during a drive cycle) and autostart commands (e.g., commands to start the engine 12 during a drivecycle). The engine 12 will be shutdown in response to auto stop commandsand will be started in response to auto start commands as known in theart.

Referring to FIGS. 1 and 2, it is determined whether vehicle speed isless than a threshold speed at operation 38. The controllers 36, forexample, can compare speed data from the sensors 34 to somepredetermined speed such as 5 miles per hour. If no, the algorithmreturns to operation 38. If yes, it is determined whether an acceleratorpedal is released or a brake pedal is pressed at operation 40. Thecontrollers 36, for example, can determine whether position dataassociated with the accelerator pedal 30 and brake pedal 32 indicatesthat the accelerator pedal 30 is released or the brake pedal 32 ispressed. If no, the algorithm returns to operation 38. If yes, it isdetermined if there are any inhibit auto stop conditions present atoperation 42. For example, the controllers 36 can check if any flagshave been set to indicate that an auto stop of the engine 12 should beprecluded. It may be determined in one instance that power demands byvarious vehicle subsystems exceed that which can be supported by thebattery 24 alone. An auto stop inhibit flag is set in response. Othersuitable/known auto stop inhibit conditions are also contemplated. Ifyes, the algorithm returns to operation 38.

Referring to FIGS. 1 and 3, if no, engine pre-shutdown protocols forvarious vehicle components and a timer are initiated at operation 44.The controllers 36, for example, can cause the intake manifold 18 to bepurged, the voltage on the electrical bus 26 to be reduced to sometarget value, the transmission 14 to be shifted, the electric pump 20 tobe activated, etc. as mentioned above. Additionally, the controllers 36can initiate a counter. At operation 46, it is determined whether theengine pre-shutdown protocols are complete. If no, the algorithm returnsto operation 46. If yes, it is determined whether vehicle speed isapproximately 0 at operation 48. For example, the controllers 36 canexamine data from the sensors 34 to determine if it suggests that speedof the vehicle 10 is approximately 0. If yes, the engine is shutdown atoperation 50. For example, the controllers 36 can cut fuel to the engine12 and take other necessary steps to stop the engine 12 as known in theart. If no, it is determined whether the timer has expired or an autostop inhibit condition is present at operation 52. The controllers 36,for example, can compare a current value of the counter to a thresholdvalue. The controllers 36 also, for example, can check if any flags havebeen set to indicate that an auto stop of the engine 12 should beprecluded as discussed above. If no, the algorithm returns to operation48. If yes, the vehicle components affected by the engine pre-shutdownprotocols are reset at operation 54. For example, the controllers 36 cancause the voltage on the electrical bus 26 to increase to the value ithad prior to initiation of the engine pre-shutdown protocols, etc. Thealgorithm then returns to operation 38 (FIG. 2).

In other implementations, all of the operations of FIG. 2 need not beperformed prior to initiating engine pre-shutdown protocols. Operations40 and 42, as an example, could be omitted. Operation 40, as anotherexample, could be omitted, etc. A similar comment applies to FIG. 3. Atimer, for example, need not be used. Other scenarios are also possible.Referring to FIG. 4, for example, it is determined whether vehicledeceleration is greater than a threshold at operation 38′. For example,the controllers 36 can derive deceleration based on speed data from thesensors 34 and compare it to a threshold value such as 10 meters persecond. If no, the algorithm returns to operation 38′. If yes, time tovehicle stop is predicted at operation 40′. The controllers 36, forexample, can derive predicted time to stop based on the speed data andthe deceleration (e.g., current vehicle speed÷current vehicledeceleration=predicted time to vehicle stop). At operation 42′, it isdetermined whether predicted time to vehicle stop is less than or equalto time to complete engine pre-shutdown protocol. Testing, simulation,etc. may be used to determine the time required to complete the enginepre-shutdown protocol for each affected vehicle component. As anexample, the time required to reduce the voltage on the electrical busfrom a current value to the desired value may be measured. As anotherexample, the time to purge the intake manifold 18 may be measured. Thevehicle component requiring the longest time to complete enginepre-shutdown activities may be used as the time to complete enginepre-shutdown protocol. The controllers 36 can, for example, compare thepredicted time to vehicle stop to the time to complete enginepre-shutdown protocol. If no, the algorithm returns to operation 38′. Ifyes, the algorithm proceeds to operation 44 (FIG. 3).

The processes, methods, or algorithms disclosed herein may bedeliverable to/implemented by a processing device, controller, orcomputer, which may include any existing programmable electronic controlunit or dedicated electronic control unit. Similarly, the processes,methods, or algorithms may be stored as data and instructions executableby a controller or computer in many forms including, but not limited to,information permanently stored on non-writable storage media such as ROMdevices and information alterably stored on writeable storage media suchas floppy disks, magnetic tapes, CDs, RAM devices, and other magneticand optical media. The processes, methods, or algorithms may also beimplemented in a software executable object. Alternatively, theprocesses, methods, or algorithms may be embodied in whole or in partusing suitable hardware components, such as Application SpecificIntegrated Circuits (ASICs), Field-Programmable Gate Arrays (FPGAs),state machines, controllers or other hardware components or devices, ora combination of hardware, software and firmware components.

While exemplary embodiments are described above, it is not intended thatthese embodiments describe all possible forms encompassed by the claims.The words used in the specification are words of description rather thanlimitation, and it is understood that various changes may be madewithout departing from the spirit and scope of the disclosure. Aspreviously described, the features of various embodiments can becombined to form further embodiments of the invention that may not beexplicitly described or illustrated. While various embodiments couldhave been described as providing advantages or being preferred overother embodiments or prior art implementations with respect to one ormore desired characteristics, those of ordinary skill in the artrecognize that one or more features or characteristics can becompromised to achieve desired overall system attributes, which dependon the specific application and implementation. These attributes mayinclude, but are not limited to cost, strength, durability, life cyclecost, marketability, appearance, packaging, size, serviceability,weight, manufacturability, ease of assembly, etc. As such, embodimentsdescribed as less desirable than other embodiments or prior artimplementations with respect to one or more characteristics are notoutside the scope of the disclosure and can be desirable for particularapplications.

What is claimed is:
 1. A stop/start vehicle comprising: an engine; anelectrical bus; and at least one controller configured to initiate areduction in voltage on the electrical bus to a predetermined value whena speed of the vehicle is greater than approximately zero and less thana predetermined speed and to initiate a stop of the engine after thespeed of the vehicle is approximately zero and the voltage isapproximately equal to the predetermined value.
 2. The stop/startvehicle of claim 6 further comprising an intake manifold in fluidcommunication with the engine and wherein the at least one controller isfurther configured to initiate a purge of the intake manifold when thespeed of the vehicle is greater than approximately zero and less thanthe predetermined speed.
 3. The stop/start vehicle of claim 6 furthercomprising an automatic transmission mechanically coupled with theengine and wherein the at least one controller is further configured toinitiate a shifting of gears of the automatic transmission when thespeed of the vehicle is greater than approximately zero and less thanthe predetermined speed.
 4. The stop/start vehicle of claim 6 furthercomprising an electric pump and wherein the at least one controller isfurther configured to initiate activation of the electric pump when thespeed of the vehicle is greater than approximately zero and less thanthe predetermined speed.